linux-kernel - Re: [PATCHv10 3/4] genirq: Avoid summation loops for /proc/interrupts

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Message-ID: <1606230b-83af-4f5f-b1ef-6ae8f73841f5@linux.alibaba.com>
Date: Wed, 28 Feb 2024 14:07:15 +0800
From: Bitao Hu <yaoma@...ux.alibaba.com>
To: Thomas Gleixner <tglx@...utronix.de>, dianders@...omium.org,
 liusong@...ux.alibaba.com, akpm@...ux-foundation.org, pmladek@...e.com,
 kernelfans@...il.com, deller@....de, npiggin@...il.com,
 tsbogend@...ha.franken.de, James.Bottomley@...senPartnership.com,
 jan.kiszka@...mens.com
Cc: linux-kernel@...r.kernel.org, linux-mips@...r.kernel.org,
 linux-parisc@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
 yaoma@...ux.alibaba.com
Subject: Re: [PATCHv10 3/4] genirq: Avoid summation loops for /proc/interrupts

On 2024/2/27 23:39, Thomas Gleixner wrote:
> On Tue, Feb 27 2024 at 19:20, Bitao Hu wrote:
>> On 2024/2/27 17:26, Thomas Gleixner wrote:
>>>
>>> and then let kstat_irqs() and show_interrupts() use it. See?
>>
>> I have a concern. kstat_irqs() uses for_each_possible_cpu() for
>> summation. However, show_interrupts() uses for_each_online_cpu(),
>> which means it only outputs interrupt statistics for online cpus.
>> If we use for_each_possible_cpu() in show_interrupts() to calculate
>> 'any_count', there could be a problem with the following scenario:
>> If an interrupt has a count of zero on online cpus but a non-zero
>> count on possible cpus, then 'any_count' would not be zero, and the
>> statistics for that interrupt would be output, which is not the
>> desired behavior for show_interrupts(). Therefore, I think it's not
>> good to have kstat_irqs() and show_interrupts() both use the same
>> logic. What do you think?
> 
> Good point. But you simply can have
> 
> unsigned int kstat_irq_desc(struct irq_desc *desc, const struct cpumask *mask)
> 
> and hand in the appropriate cpumask, which still shares the code, no?
> 
Alright, that is a good approach.